The invention relates to an information recording and/or reading system comprising an interchangeable disc unit for holding recorded information and a drive unit for manipulating the disc unit. The interchangeable disc unit comprises a disc pack including at least one information disc, a polygonal enclosure including first and second covers for containing the disc pack, and connecting means for interconnecting the two covers. The two covers engage with each other and are movable relative to each other from a closed position to an operating position. At least one of the covers has a central opening for the passage of means for rotary drive of the disc pack when the covers have been moved from the closed position to the operating position. The connecting means comprise connecting devices attached to the covers near corners thereof.
The drive unit comprises a drive device, an information recording and/or reading apparatus and a cover displacement device. The drive device, which is rotatable about an axis of rotation for the rotary drive of the disc pack, comprises a drive spindle provided with means for centering and supporting the disc pack on the drive spindle. The information recording and/or reading apparatus, which is utilized for recording information on and/or reading information from a disc pack placed on the drive device, comprises a recording and/or reading head which is radially movable relative to the axis of rotation of the drive device. The cover displacement device is utilized for moving the two covers of a disc unit placed on the drive unit relative to each other between the closed position and the operating position.
Such a system is disclosed in German patent specification No. 1,524,974 to which U.S. Pat. No. 3,487,390 corresponds. In this system the disc pack comprises three magnetic information discs contained in an enclosure of cylindrical shape. The enclosure comprises an upper cover with a central recess in which a handle is located, and has a cylindrical side wall and a flat lower cover, which is connected to a hub. The three information discs are mounted on the hub. The hub extends into the interior of the disc unit over the full height of the enclosure. The handle in the center of the upper cover comprises connecting means adapted to connect the upper cover to the hub of the disc pack and thus to the lower cover.
The drive unit comprises a hinged cover at its top which is swung open when a disc unit is to be placed thereon. By means of the handle in the upper cover a disc unit is manually placed onto the drive device of the drive unit. The lower cover of the disc unit leaves the center portion of the hub free, so that the hub can be lowered freely onto the drive spindle, where it is centered by the centering means and supported by the supporting means. A push rod is axially movable into the center of the drive spindle. The handle in the upper cover is designed so that the connecting means can be actuated through the hub of the disc pack by means of the push rod. When the hinged cover of the drive unit is closed the push rod is axially moved in the drive spindle, by means of a system of cables, pulleys and levers, in order to release the upper cover. Subsequently the upper cover is axially moved relative to the lower cover and thus relative to the disc pack into its operating position. The push rod returns to its original position and the disc pack together with the lower cover is rotated by the drive unit.
An information recording and/or reading apparatus comprises a plurality of arms which are radially movable relative to the axis of rotation of the drive device. The arms can be moved toward the disc pack so that magnetic heads, which are mounted on the ends of the arms, can cooperate with the information discs. If the disc unit is to be removed from the drive unit, the operations described in the foregoing are performed in a reverse order by opening the cover. By means of the system of cables, pulleys and levers the upper cover is lowered onto the disc pack and subsequently the upper cover is reconnected to the hub and thus to the lower cover. The disc pack can be manually removed from the drive unit by means of the handle.
The disc units for this information recording and/or reading system thus have comparatively intricate connecting means and the drive units have the drawback that a push rod which is axially movable through the spindle must be provided in order to release the connecting means from the disc unit.
A further disadvantage with the disc unit is that the lower cover rotates along with the information disc during operation. As a result of this, the disc pack is not suitable for cooperation with an optical information recording and/or reading apparatus which is adapted to cooperate with an information disc at the underside and which is radially movable relative to the drive spindle on the deck of a drive unit.
U.S. Pat. No. 4,151,572 describes another disc unit of the type defined in the opening paragraph, which unit is of a substantially square shape in a view at the covers. The connecting means comprise either identical levers with associated compression springs. Near each of its four corners each cover is provided with a bearing pin for a lever, which pin extends perpendicularly to the cover, so that said lever is pivotable to a limited extent in a direction parallel to the covers. The levers are arranged symmetrically relative to the center of the enclosure and identically for both covers. The bearing pins are located at a small offset from the diagonals of the cover. The levers each comprise a free end with an oblique face. On fitting the covers on each other, the oblique surfaces at the free ends of the levers on the first cover cooperate with those of the levers on the second cover, so that the levers, against spring pressure, are pivoted out and are subsequently pivoted back. In the pivoted-back positions the levers on the one cover hook behind the levers on the other cover at their free ends, so that the covers are interconnected. For releasing the covers they are formed with openings near the corners, enabling release pins of a drive unit to be introduced in an axial direction. The release pins slightly pivot the four levers on the cover through which the release pins extend against spring pressure, so that the free ends of the levers no longer cooperate with each other. After this the covers can be moved relative to each other to the operating position.
The connecting means of this disc unit comprise a comparatively great number of separate parts, namely eight levers and eight compression springs as well as eight retainers for the levers on the bearing pins The bearing pins should be strong and the levers should be journalled on said pins with a comparatively small clearance. The disc unit can be opened in a comparatively easy manner by unauthorized persons. For this purpose it suffices to pivot a lever at every corner through a small angle via the opening in the cover. A small axial displacement of the covers relative to each other is then sufficient to separate the covers from each other. In many cases this will be possible because of the elasticity of and the clearance between the covers.
A further disadvantage with the known disc unit is that the lower cover rotates along with the information disc during operation. As a result of this, the disc pack is not suitable for cooperation with an optical information recording and/or reading apparatus which is adapted to cooperate with an information disc at the underside and which is radially movable relative to the axis of rotation of the disc pack.